3 major chains that together own more than 2,000 stores, along with a handful of smaller chains, promise not to carry genetically engineered salmon.

By now, you’ve probably heard that the FDA will mostly likely approve the first genetically engineered fish to be sold in grocery stores. AquAdvantage salmon is a breed of salmon that’s been genetically altered to grow twice as fast as regular salmon.

One of the major concerns that consumers have is that there is no indication that the FDA will require this "Frankenfish," as some call it, to be labeled as genetically engineered. Supermarkets could sell it alongside of, or instead of, natural salmon, and shoppers would be none the wiser.

Food Safety News reported yesterday that three major supermarket chains — Whole Foods, Trader Joes and Aldi — took part in a pledge as part of the Campaign for GE-Free Seafood. They announced that they will not sell genetically engineered salmon.

The three chains collectively own more than 2,000 grocery stores across the United States, a little more than 5 percent of all full-service supermarkets. In addition to the these major chains, Marsh Supermarkets in Indiana and Ohio, PCC Natural Markets in Washington state, and various co-ops in California, New York, Minnesota and Kansas have all taken the pledge.